Grundfos MAGNA3 25-80 Installation And Operating Instructions Manual page 23

7.3.3 FLOW
ADAPT
The FLOW control mode combines AUTO
ADAPT
FLOW , meaning that the pump runs AUTO
LIMIT
same time ensuring that the flow never exceeds the entered
FLOW value. This control mode is suitable for systems
LIMIT
where a maximum flow limit is desired and where a steady flow
through the boiler in a boiler system is required. Here, no extra
energy is used for pumping too much liquid into the system.
In systems with mixing loops, you can use FLOW
the flow in each loop.
Characteristics and key benefits
• The dimensioned flow for each zone (required heat energy) is
determined by the flow from the pump. This flow can be set
precisely in the FLOW
ADAPT
throttling valves.
• When the flow is set lower than the balancing valve setting,
the pump will ramp down instead of losing energy by pumping
against a balancing valve.
• Cooling surfaces in air-conditioning systems can operate at
high pressure and low flow.
Note: The pump cannot reduce the flow on the inlet side, but is
able to control that the flow on the outlet side is at least the same
as on the inlet side. This is due to the fact that the pump has no
built-in valve.
Technical specifications
H
25 % Q
max
Setting range
H
fac
H
auto_min
Fig. 26 FLOW control
ADAPT
The factory setting of the FLOW
AUTO factory setting meets the maximum curve. See fig.
ADAPT
26.
The typical pump selection is based on the required flow and
calculated pressure losses. The pump is typically oversized by 30
to 40 % to ensure that it can overcome the pressure losses in the
system. Under these conditions, the full benefit of AUTO
cannot be obtained.
To adjust the maximum flow of this "oversized" pump, balancing
valves are built into the circuit to increase the resistance and thus
reduce the flow.
The FLOW function reduces the need for a pump throttling
ADAPT
valve, see fig. 27, but does not eliminate the need for balancing
valves in heating systems.
Fig. 27 Reduced need for a pump throttling valve
and
ADAPT
while at the
ADAPT
to control
ADAPT
control mode without using
90 % Q
max
Q
Q
fac
is the flow where the
ADAPT
ADAPT
7.3.4 Proportional pressure
Proportional pressure is suitable in systems with relatively large
pressure losses in the distribution pipes and in air-conditioning and
cooling systems:
• Two-pipe heating systems with thermostatic valves and the
following:
– very long distribution pipes
– strongly throttled pipe balancing valves
– differential-pressure regulators
– large pressure losses in those parts of the system where the
total quantity of water flows (for example boiler, heat
exchanger and distribution pipe up to the first branching).
• Primary circuit pumps in systems with large pressure losses in
the primary circuit.
• Air-conditioning systems with the following:
– heat exchangers (fan coils)
– cooling ceilings
– cooling surfaces.
Characteristics and key benefits
• The head of the pump increases proportionally to the flow in
the system.
• Compensates for large pressure losses in the distribution
pipes.
Technical specifications
H
H
set
H
set
2
Fig. 28 Proportional-pressure control
The head is reduced at decreasing flow demand and increased at
rising flow demand.
The head against a closed valve is half the setpoint H
set the setpoint with an accuracy of 0.1 metre.
Q
. You can
set
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